In a process of continuously casting metal strips, such as ribbons, it is common practice to dispense the molten metal through a nozzle onto a moving chilled substrate. The molten metal solidifies soon after contact with the chilled substrate. A cast product having an amorphous molecular structure, in the form of a relatively thin elongated strip or ribbon, has proven to be effective for winding into highly efficient cores of electrical transformers, and other uses. Recent developments in the casting of amorphous metal strips are reviewed in U.S. Pat. No. 4,332,848.
The ribbon may be transported a substantial distance during the quenching process before it is delivered to other processing equipment, such as measuring or winding equipment. In one arrangement, the ribbon is transported on top of a moving belt substrate. In such circumstances, the ribbon exhibits a tendency to shift on the rapidly moving belt during transport.
In one advantageous casting technique, the cast ribbon is deposited onto the upper run of an endless belt adjacent or directly above an end roller. The belt quickly travels about the end roller to position the cast ribbon upside down on the lower run of the belt. Since the ribbon then clings to the belt against gravity bias, there is an even greater tendency for the ribbon to shift or even fall off the belt. Regardless as to whether the ribbon is transported on top of the belt or on the lower run of the belt, the premature departure of the ribbon from its preferred position on the belt has deleterious consequences.
It has been proposed that ribbons cast of ferromagnetic material may be retained on a casting belt by magnetic attraction. A line of magnets is positioned proximal to an inner face of the belt (opposite the casting surface). The casting belt may be formed of ferromagnetic, paramagnetic or non-magnetic material. If the belt is formed of paramagnetic or non-magnetic material, the magnetic attraction force is then applied through the casting belt to retain the ribbon against the belt. If, however, the belt is formed of ferromagnetic material, both the belt and the ribbon are attracted toward the magnets. In either case, the ribbon is prevented from prematurely departing from the belt. The strength of the magnetic field is designed to exceed the inertial and gravitational forces urging the ribbon off the belt.
The use of magnets cooperating with delivery belts to cause ferrous metal sheet material to adhere to a belt for transport is disclosed in U.S. Pat. No. 3,315,958. In this patent, elongated stationary skids of non-magnetic material are interposed between the belts and the magnets. These stationary skids extend along the entire belt/magnet interface, separating the belts from the magnets and serving as a rigid bearing surface for facilitating belt movement of the belts.
The use of skids along the entire belt/magnet interface results in excessive frictional forces. The frictional forces becoming particularly pronounced as the retention length of the belt increases. As a result, substantial power is required for moving the belt. Furthermore, the excessive frictional forces generated by the belt movement adversely affects the smoothness of belt movement and causes premature belt wear.